I think dave is right and you need to work from as much reference material as you can find. I would then try to stick to one part for as long as possible. For instance work on the head then torso then arms etc etc, trying to get each piece of anatomy correct. With some reference material though you will probably find it much easier to make these adjustments plus you should get better results. Also would it be possible to see a wireframe of your model to see if there are any problem areas.

Good luck and keep at it